Why I get the console warning: [Process] kill() returned unexpected error 1 when I load a WKWebView in iOS13.2?

It's a bug in WebKit (or the underlying OS itself). And no, it was not fixed in 13.[2,3] release.

see:

• https://bugs.webkit.org/show_bug.cgi?id=202173
• https://www.mail-archive.com/[email protected]/msg146193.html

Update:

It's fixed in 13.4 release.

As in the accepted answer, this is a WebKit bug and it seems that it has been fixed but not released up until the latest iOS release 13.2.2 (at the time of writing this answer) has been fixed in iOS 13.4.

As a workaround, however, you can disable/hide the logs temporarily as mentioned in an answer by @iDevzilla:

1- From Xcode menu open: Product > Scheme > Edit Scheme

2- On your Environment Variables set OS_ACTIVITY_MODE = disable

This will ONLY hide the logs so you can continue developing and testing on iOS. As some indicated, this problem crashes their apps no matter what (for me it is not until now). Also, be careful using this method as it might hide important error messages!

iOS 13.4 has removed this error! Hurray!